1. Field of the Invention
The present invention relates to a method and apparatus for measuring particles, and more particularly to a method and apparatus which utilizes the scattering characteristics of light scattering from a fluid and from particles in the fluid to measure the diameter and/or quantity of the particles.
2. Description of the Prior Art
Various methods are known for detecting particles contained in a fluid. In particular, techniques using scattered light that permit such measurements to be carried out on an inline, continuous basis are applied in a broad range of fields. In semiconductor manufacturing processes in particular, the increasing density of large-scale integrated circuits (LSI) has increased the importance of cleaning technology for removing foreign particles that have adhered to wafers in the course of LSI fabrication.
However, the chemicals used on the wafers contain particles of foreign matter that can adhere to the wafer, giving rise to LSI malfunctions, short-circuits and other such problems. This being the case, it is necessary to reduce foreign particles in cleaning chemicals, so measuring the diameters or quantities of these particles in the fluids concerned has therefore become important.
A conventional measurement apparatus that utilizes scattered light detects particles contained in a fluid by projecting a beam of light at the fluid and measuring and analyzing the intensity of scattered light that is received, with no spectral separation of the scattered light being applied.
However, the scattered light thus measured includes light scattered by particles and light scattered by the fluid itself. The light scattered by the fluid has a strong background effect that makes it increasingly difficult to detect particles as the size of the particles decreases.